1. Field of the Invention
The present invention relates to an antenna system. More particularly, the present invention relates to an antenna system having an antenna kept in a certain direction with respect to a gravity direction.
2. Description of the Related Art
Generally, a signal transmitting/receiving circuit transmits and receives a signal using an antenna during signal transmission. The signal transmitting/receiving circuit is provided in a Base Station (BS), a Relay Station (RS) and a Mobile Station (MS).
The antenna is a device for transmitting and receiving a signal via a free space, such as an air interface, for radio communications.
FIG. 1 is a schematic diagram illustrating a ship transmitting and receiving a signal through a conventional antenna.
Referring to FIG. 1, the ship is placed at sea level and is equipped with an antenna, which is connected to a signal transmitting/receiving circuit provided on the ship to transmit and receive a signal.
Since the antenna of the signal transmitting/receiving circuit is fixed to the ship along with the signal transmitting/receiving circuit, the antenna moves according to movement of the ship, which may be caused by waves or the like.
In general, an antenna forms a beam in a particular direction, wherein the formed beam refers to a direction, shape and position of specific electromagnetic waves which can transmit and receive a signal. In particular, the beam has a specific orientation and shape, and the shape of the beam is referred to as a beam pattern or a radiation pattern.
The signal transmitting/receiving circuit transmits and receives a signal through the antenna. Namely, the signal transmitting/receiving circuit detects a signal through beams of the antenna.
In general, antennas include a non-directional antenna and an omni-directional antenna. The non-directional antenna forms beams in all directions, for example, from an upper direction to a lower direction with respect to the antenna, and a type of the non-directional antenna is an isotropic antenna. However, the isotropic antenna is a so-called theoretical antenna, and therefore, most of the antennas have a beam pattern.
One example of the antennas, which have a beam pattern, is an omni-directional antenna. The omni-directional antenna has a beam pattern which spreads evenly sideways, rather than in an upper direction or a lower direction, and therefore, is effective for use at the ground level.
Herein, it is assumed that the antenna discussed below is an omni-directional antenna.
The antenna provided on the ship forms beam patterns 111 and 113 corresponding to its orientation which changes due to waves.
As illustrated in FIG. 1, reception signals which will be received via the antenna are indicated by arrows. In FIG. 1, it is noted that beam patterns 111 and 113 are not formed in such a direction that the reception signals are correctly received due to movement of the antenna. Thus, signal transmitting/receiving ability of the antenna becomes deteriorated.
Therefore, a need exists for an antenna for forming a correct beam pattern in response to movement of the antenna, thereby improving the signal transmitting/receiving ability.